Conventionally, external connection busbars that are connected to the output electrode terminals of a group of power storage elements have been known, such as that described in JP 2014-127229A. This reference discloses a battery module (power storage module) M1 in which two electrode terminals of the power storage elements at both ends of a power storage element group serve as a pair of output electrode terminals. The battery module M1 also includes external connection busbars 19B connected to the aforementioned electrode terminals of the power storage elements at both ends. The external connection busbars 19B as well as busbars 19 that are connected to the electrode terminals of the power storage elements are protected by a resin protector 20.
JP 2014-127229A is an example of related art.
However, if the arrangement of a plurality of power storage elements of the group of power storage elements is the same as that disclosed in JP 2014-127229A, that is, if the power storage elements that have a thin rectangular solid shape are arranged in a thickness direction, pin a power storage module in which a group of power storage elements are arranged in the same manner as disclosed in the above-identified reference, that is, if the power storage elements in a shape of a thin rectangular solid are arranged in the direction of their width, power may be supplied to an external device from the same end of the power storage element group to an external device via the external connection busbars. In this case, one of the external connection busbars connected to one of the paired pair of output electrode terminals needs to be routed over a long distance to the other end of the power storage element group. This means that this arrangement requires an elongated external connection busbar and a holder member that supports the elongated external connection busbar.
Additionally, an external connection member such as an external device connection busbar for enabling connection to an external device powered by the power storage element group is often bolted to each of the external connection busbars. In order to absorb product variations, predetermined clearances (gaps) are often provided between the external connection busbar holder member and the locking members for locking the holder member. In this case, when the external connection member is bolted to an external connection busbar that is connected to the other one of the output electrode terminals, the aforementioned clearances may allow rattling (displacement) in the holder member. In other words, the clearances make it more likely that the rotation of the bolts will generate a torque load, and the generated torque load will act on the connections between the external connection busbars and the output electrode terminals via the holder member. Such a torque load may affect the reliability of the connection between the external connection busbars and the output electrode terminals of the power storage element group.